- Date
- October 2, 2017, 08:40 local (13:40 UTC)
- Place
- Chicago, IL
- Injuries
- 84 uninjured
- Damage
- Substantial damage
- Phase of flight
- Prior to flight
- Aircraft
- N930WNBoeing 737 7H4
- Defining event
- Prior to flight: Ground handling event
- Weather
- Visual (VMC) · Day
- Status
- Completed · report June 8, 2020
- Report
- Approved by Office Director
- NTSB office
- Major Investigations Division
- FAA report
- 20171002014309A
- Case key
- 96133
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.
On this page
Probable cause
the mechanical failure of the tugs fuel governor, which made it difficult for the ramp agent to stop the tug. Contributing to the accident was the lack of guidance on how ground personnel were to handle vehicle malfunctions.
Findings · 2
NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.
Sequence of events
The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.
Analysis
On October 2, 2017, at about 0840 CDT, Southwest Airlines flight 681, Boeing B737-700, N930WN, was struck by an unmanned tug while boarding was ongoing at Chicago Midway Airport (KMDW), Chicago, Illinois. There were no injuries to the 84 passengers and crew onboard. The airplane received substantial damage to the lower fuselage skin, frames and stringers over an area about 3 feet by 3 feet. The flight was operating under 14 Code of Federal Regulation Part 121 as a scheduled passenger flight from KMDW to Omaha Airport (KOMA), Omaha, Nebraska. A ramp agent was driving a covered baggage tug with two baggage carts in tow between Gates B22 and B24 when the tug made contact with two staged baggage carts. The ramp agent jumped off the tug as the tug continued to accelerate forward. The now unmanned baggage tug struck additional ground support equipment before striking the fuselage of the accident airplane at Gate B22. The ramp agent stated afterwards that he could not get the tug to stop and thought running the tug into the staged baggage carts would stop or at least slow the tug down. Examination of the baggage tug after the event revealed there was a mechanical failure of the fuel governor which resulted in the runaway. The runaway could have been stopped by either turning the ignition key off or using the manual shut down lever on the front cover. There was no guidance in the Ground Operations Training Manual related to how ramp personnel should handle mechanical failures of ground support equipment.
Factual narrative
On October 2, 2017, at about 0840 CDT, Southwest Airlines flight 681, Boeing B737-700, N930WN, was struck by an unmanned tug while boarding was ongoing at Chicago Midway Airport (KMDW), Chicago, Illinois. There were no injuries to the 84 passengers and crew onboard. The airplane received substantial damage to the lower fuselage skin, frames and stringers over an area about 3 feet by 3 feet. The flight was operating under 14 Code of Federal Regulation Part 121 as a scheduled passenger flight from KMDW to Omaha Airport (KOMA), Omaha, Nebraska. A ramp agent was driving a covered baggage tug with two baggage carts in tow between Gates B22 and B24 when the tug made contact with two staged baggage carts. The ramp agent jumped off the tug as the tug continued to accelerate forward. The now unmanned baggage tug struck additional ground support equipment before striking the fuselage of the accident airplane at Gate B22. The ramp agent stated afterwards that he could not get the tug to stop and thought running the tug into the staged baggage carts would stop or at least slow the tug down. Examination of the baggage tug after the event revealed there was a mechanical failure of the fuel governor which resulted in the runaway. The runaway could have been stopped by either turning the ignition key off or using the manual shut down lever on the front cover. There was no guidance in the Ground Operations Training Manual related to how ramp personnel should handle mechanical failures of ground support equipment.
Aircraft
- Registration
- N930WN
- Reported as
- Boeing 737 7H4 (7H4)
- Category
- Airplane
- Serial number
- 36636
- Built
- 2009
- Airframe hours
- 30,104
- Engines
- CFM International CFM56-7B24, turbo fanCFM International CFM56-7B24, turbo fan
- Damage
- Substantial damage
- Flight
- Part 121
- Operator
- Southwest Airlines
- Registered owner
- Wells Fargo Bank Northwest Na Trustee
- Airworthiness certificate
- Standard, Transport
- Last inspection
- September 27, 2017
- Departed
- KMDW · Chicago, IL
- Destination
- KOMA · Omaha, NE
- Flight plan
- IFR
- Airport
- KMDW · Chicago Midway International A
- Equipment
- Electronic primary flight display, Electronic multifunction display, Electronic flight bag or handheld device, Data recorder, Heads up display, Onboard weather, Stall warning system
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 190° at 9 knots
- Visibility
- 10 statute miles
- Lowest ceiling
- 7,000 ft broken
- Temperature
- 68 °F, dew point 52 °F
- Altimeter
- 30.19 inHg
- Observed at
- KMDW
Docket · 2
The files NTSB released with the investigation on July 14, 2020, on NTSB’s docket system: statements, records, photos and specialists’ reports. 10.9 MB in all.
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.